When Laying Grass Sod, Does It Require Dirt as a Base?

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Installing sod allows you to establish a new lawn without the variance and hassle sometimes associated with growing grass from seed. For sod to become established in your lawn, it needs to develop deeper roots to anchor it in place. For best results, sod needs bare soil as a base so its roots aren't impeded as they attempt to grow deeper.

Sod Base

The base for your sod is the material that the sod grass roots will grow into, and soil that has been prepared in advance provides the best base. While it is possible to lay sod over existing grass instead of prepared soil, the grass can interfere with proper root development and cause the sod to come loose easily or dry out. Other base materials such as sand or clay-heavy soil are also not recommended since your sod may have trouble getting all of the water that it needs. Concrete or other solid materials cannot be used because the roots will be unable to penetrate and anchor the sod.

Preparing the Soil

If the soil is packed hard or lacking in nutrients, your sod may still have trouble becoming established. Cultivating the soil to a depth of 6 to 8 inches ensures that the topsoil isn't packed, and amending it with 2 to 3 inches of compost adds organic material that provides nutrients and aids water retention. If the soil contains large quantities of clay, you can also add sand as needed to improve drainage so water will penetrate deeper into the soil. Once cultivation and amendments are complete, a metal rake should be used to level the soil at 1 inch below any sidewalks, driveways or other fixtures in your yard.

Laying the Sod

Sod should be purchased as close to the time you lay it as possible, preferably having it delivered on the day that you begin installing it. During the summer, water the soil just before laying the sod to cool it down, preventing possible transplant shock that might otherwise occur from laying sod over hot base soil. Lay the sod one row at a time, cutting the second row in half to create a staggered seam pattern similar to laying bricks. Once the sod is installed, water it thoroughly to stimulate the roots and settle the sod onto the underlying soil.

Root Development

Grass roots seek out moisture, so it's important that you water your sod sufficiently during the establishment period to encourage deep root development. Use a moisture probe if necessary to check how deep the water goes. During early establishment you should thoroughly water the sod every morning, switching to every other day after the first week. Reduce watering to twice a week after the third week, then switch to 1 inch of water per week by the fourth week as deep roots should already be developing.

About the Author

Born in West Virginia, Jack Gerard now lives in Kentucky. A writer and editor with more than 10 years of experience, he has written both articles and poetry for publication in magazines and online. A former nationally ranked sport fencer, Gerard also spent several years as a fencing coach and trainer.